1. Field of the Invention
This invention relates to a highly water-resistant adhesive which firmly adheres to hard tissues of the living body such as teeth and bones, metallic materials, organic polymeric materials, and ceramics. The "adhesive" as used herein not only denotes compositions used to bond adherends to one another but also encompasses compositions which are used to form a highly adhesive coating layer on the surface of adherends such as metallic materials and organic polymeric materials or used to form a highly adhesive filling material for repairing hard tissues of the living body. In other words, by "adhesive" is meant any and all compositions which are applicable for adhesion to a variety of substances including hard tissues of the living body, metallic materials, organic polymeric materials, and ceramics.
2. Description of the Prior Art
A variety of metallic materials, organic polymeric materials, and ceramic materials are in use as restorative dental materials. When in use, these materials are required to firmly adhere to teeth and/or to one another. Moreover, they are required to exhibit adhesion under the wet conditions of the mouth.
Heretofore, many attempts have been made to use a phosphoric ester compound as an adhesive in the dentistry. For example, U.S. Pat. Nos. 4,259,075, 4,259,117, and 4,368,043 disclose that a polymerizable composition containing a vinyl compound having a group of the formula ##STR2## is useful as a dental adhesive. U.S. Pat. No. 4,222,780 also teaches that a polymerizable composition containing a vinyl compound having a group of the formula ##STR3## is useful as a dental adhesive. In fact, some of the compositions defined in these patents have found practical use as a primer to be applied to the wall of a tooth cavity, prior to filling thereof. The compositions disclosed in the above-mentioned patents, however, have the drawback that they do not firmly adhere to a tooth unless the surface of the tooth cavity previously undergoes acid etching. In addition, they do not firmly adhere to an Ni--Cr alloy which is a common dental metallic material.
Attempts have also been made to prepare a dental adhesive from a polymerizable phosphoric ester compound as mentioned below.
(i) U.S. Pat. No. 3,882,600 discloses phosphoryl monofluoride. PA0 (ii) There are shown CH.sub.2 .dbd.CH--PO(OH).sub.2 and CH.sub.2 .dbd.CHC.sub.6 H.sub.4 CH.sub.2 P--O(OH).sub.2 in the Journal of Dental Research, Vol. 53, p. 878-888 and Vol. 56, p. 943-952; Chemical Abstract, Vol. 77, p. 290 (66175g); and Japanese Patent Laid-open No. 44152/1976. PA0 (iii) Japanese Patent Laid-open No. 113843/53 discloses a compound of the formula ##STR4## (where R is an organic residue having at least one vinyl group), with one of the two OH groups being neutralized. Said patent exemplifies the following compounds, in which M denotes a metal. ##STR5## (iv) Japanese Patent Publication No. 49557/1982 discloses methacryloyloxyethane-1,1-diphosphonic acid of the formula ##STR6## PA0 X.sub.1, X.sub.1 ', X.sub.2, and X.sub.2 ' denote O, S, or NR.sub..alpha. [where R.sub..alpha. is H or a C.sub.1-6 alkyl group], PA0 m is an integer of 1 to 4, PA0 n is an integer of 0 to 4, PA0 k and k' are 0 or 1, PA0 R.sub.a is a C.sub.8-40 organic residue having a valence of (m+1), and PA0 R.sub.a ' is a C.sub.1-40 organic residue having a valence of (n+1)); and PA0 (i) a hydrocarbon group which may have an OH group, COOH group, NH.sub.2 group, or halogen (F, Cl, Br, or I) as a substituent group, and PA0 (ii) a group composed of a plurality (2 to 20) of hydrocarbon groups which may have the above-mentioned substituent group, said hydrocarbon groups being connected to one another through the linkage of the type of ether, thioether, ester, thioester, thiocarbonyl, amide, carbonyl, sulfonyl, urethane, ##STR10## PA0 [C.dbd.C]--A.sub.1 --[P--P]--A.sub.2, [C.dbd.C]--A.sub.1 --B.sub.1 --A.sub.2 --B.sub.2 --A.sub.3 --[P--P]--A.sub.1 '--B.sub.1 '--A.sub.2 '--B.sub.2 '--A.sub.3 --[C.dbd.C], ##STR13## PA0 (i) --CH.sub.2 --.sub.i [where i is a natural number from 8 to 20.] ##STR16## [where l is 2, 3, or 4.] ##STR17## [where p is 0 or 1, and R.sub.6 is a C.sub.5-16 hydrocarbon group.] PA0 Organophosphorus Compounds, by G. M. Kosolapoff, published by Wiley, 1950. PA0 Organophosphorus Monomers and Polymers, by Ye. L. Gefter, published by Pergamon Press, 1962 PA0 Modern Organic Synthesis Series 5, Organic phosphorus compounds, edited by The Society of Synthetic Chemistry, Japan, published by Gihodo Bellstein (Springer-Verlarg) PA0 (i) Hard tissues of the living body, such as teeth and bones. PA0 (ii) Base metals and alloys thereof such as iron, nickel, chromium, cobalt, aluminum, copper, zinc, tin, stainless steel, and brass; and noble metal alloys containing 50 to 90% of gold or platinum, which are difficult to bond with a conventional adhesive. PA0 (iii) Ceramics such as glass, porcelain, silica, and alumina. PA0 (iv) Organic polymers such as polymethyl methacrylate, polyester, polyamide, polyurethane, polycarbonate, polysulfone, and polystyrene.
All of the compounds set forth above do not exhibit high adhesive strength (particularly to a metal) when used under a wet condition.
Japanese Patent Laid-open Nos. 131799/1982 and 164171/1982 disclose as a component of dental adhesive a pyrophosphate derivative having a polymerizable functional group and a group of the formula ##STR7## or preferably a pyrophosphate derivative of the formula ##STR8## where R.sup.1 denotes an allyl, methacryloyloxy (lower) alkyl, or dimethacryloyloxy (lower) alkyl; and R.sup.2 denotes an allyl, methacryloyloxy (lower) alkyl or aryl; the (lower) alkyl in R.sup.1 and R.sup.2 may be substituted with a hydroxyl group; the lower alkyl has 6 or less carbon atoms. The patents claim that the compound increases the adhesive force for the enamel of human teeth. However, they do not mention anything about the adhesion to metals. In fact, the inventors' follow-up study showed that the compound does not significantly increase the water resistance of their adhesive strength where attached to metals.
In the industrial field, many attempts have been made to use a phosphoric ester compound as an adhesive. For example, such compounds are proposed as adhesives in U.S. Pat. Nos. 3,754,972, 3,884,864, 3,987,127, 4,001,150, 4,044,044, and 4,223,115; Japanese Patent Laid-open Nos. 20238/1974, 100596/1975, 125182/1976, 12995/1978, 11920/1981, and 44638/1982; and Japanese Patent Publication Nos. 4126/1980 and 4790/1980. However, the phosphoric ester compounds described in these patents are not necessarily satisfactory in terms of the water resistance of their adhesive strength.